diff -r be944660c56a -r 3d72ae0968f4 wp/wp-admin/includes/class-wp-upgrader-skin.php
--- a/wp/wp-admin/includes/class-wp-upgrader-skin.php	Wed Sep 21 18:19:35 2022 +0200
+++ b/wp/wp-admin/includes/class-wp-upgrader-skin.php	Tue Sep 27 16:37:53 2022 +0200
@@ -165,7 +165,7 @@
 	/**
 	 * @since 2.8.0
 	 *
-	 * @param string|WP_Error $errors
+	 * @param string|WP_Error $errors Errors.
 	 */
 	public function error( $errors ) {
 		if ( ! $this->done_header ) {
@@ -186,26 +186,27 @@
 
 	/**
 	 * @since 2.8.0
+	 * @since 5.9.0 Renamed `$string` (a PHP reserved keyword) to `$feedback` for PHP 8 named parameter support.
 	 *
-	 * @param string $string
-	 * @param mixed  ...$args Optional text replacements.
+	 * @param string $feedback Message data.
+	 * @param mixed  ...$args  Optional text replacements.
 	 */
-	public function feedback( $string, ...$args ) {
-		if ( isset( $this->upgrader->strings[ $string ] ) ) {
-			$string = $this->upgrader->strings[ $string ];
+	public function feedback( $feedback, ...$args ) {
+		if ( isset( $this->upgrader->strings[ $feedback ] ) ) {
+			$feedback = $this->upgrader->strings[ $feedback ];
 		}
 
-		if ( strpos( $string, '%' ) !== false ) {
+		if ( strpos( $feedback, '%' ) !== false ) {
 			if ( $args ) {
-				$args   = array_map( 'strip_tags', $args );
-				$args   = array_map( 'esc_html', $args );
-				$string = vsprintf( $string, $args );
+				$args     = array_map( 'strip_tags', $args );
+				$args     = array_map( 'esc_html', $args );
+				$feedback = vsprintf( $feedback, $args );
 			}
 		}
-		if ( empty( $string ) ) {
+		if ( empty( $feedback ) ) {
 			return;
 		}
-		show_message( $string );
+		show_message( $feedback );
 	}
 
 	/**